Method for supplementing amino acid levels in ruminant animals

ABSTRACT

A method for supplementing the amino acid levels in ruminants is provided where rumen-protected amino acids, particularly lysine and/or methionine, are used to supplement ruminant feed.

This application is a Continuation-in-Part of application Ser. No. 08/427,718, filed Apr. 21, 1995, now U.S. Pat. No. 5,720,970, and is also a Continuation-in-Part of application Ser. No. 08/200,490, filed Feb. 23, 1994, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for supplementing amino acids in ruminant animals. More specifically, the present invention relates to a method wherein a rumen-protected feed additive composition comprising lysine and/or methionine is added to feed which is then fed to the ruminant prior to or after calving and continuing into the ruminant's lactation period. This method increases the digestible amino acids available in the feed and positively increases the milk production of ruminants who are fed the additive. The method also improves ruminant health and appetite.

2. Description of the Background Art

A ruminant is an animal which possesses a complex stomach consisting of four morphologically distinct compartments. These compartments are rumen, reticulum, omasum and abomasum. The former two are derived from the terminal portion of the esophagus, and only the latter two are considered to be a genuine stomach. After passing the first two compartments, the food is returned to the mouth. The rumen and the reticulum are fermentation compartments wherein Ophryoscolex diplodinium and Plectridium cellulolyticum are commensal, and the digestion of the feed (vegetable tissues) is conducted by cellulase, amylase, or cellobiose secreted by these microorganisms (digestive symbiosis).

In ruminant animals like cattle or sheep, there is a problem that occurs when a biologically active substance is, for instance, orally administered: a substantial part of the substance (e.g., proteins, amino acids, etc.) are decomposed to ammonia or carbon dioxide gas by microorganisms in the rumen, making it difficult or impossible for the animal to effectively utilize all of the administered proteins and amino acids contained in feed, etc. Thus, a ruminant only receives the benefit of a portion of the nutrients fed to it and loses a portion to the support and formation of rumen microorganisms. While the nutrients (proteins, etc.) contained in feed clearly contribute to a ruminant's sustenance, another source of nutrition for ruminants is the protein derived from those microorganisms in the rumen which are passed to the lower stomachs. Accordingly, it is important to maintain the microorganism population in the rumen in order to provide a constant source of this protein.

When special nutrients or drugs which must be absorbed or metabolized are administered to ruminants it is important to protect these substances from the environmental conditions in the first stomach: i.e., from decomposition by microorganisms and from the influence of weakly acidic or weakly alkaline pH, so that the substance can be maintained intact until it reaches the intended digestive or absorptive site. Namely, it is desirable that certain nutrients and drugs pass through the rumen to the omasum without being affected by microorganisms, digestion being conducted in the abomasum with the digested feed being absorbed by the small intestine. Nutrients, etc., protected in such a manner are well known in the art and are described in U.S. Pat. Nos. 4,976,976, 4,937,083, 3,619,200, 5,093,128, 4,837,004, 3,959,493, 4,842,863, 5,023,091, 4,957,748, 4,797,288, 5,064,665, and 5,244,669 and 5,227,166 all of which are incorporated herein by reference, and Japanese Laid-Open patents 59-66842, 58-175449, 56-154956, 63-317053, 60-168351, 59-198946, 02-027950, 02-128654, 02-128655, 03-05-8755, 03-155756, 03-155757, 04-079844 and 05023114 also incorporated herein by reference.

All proteins present in animals are constituted by combinations of more than 20 different amino acids. Among these, ten "essential" amino acids are not adequately synthesized in the animal body, and the animals must take them in. The amino acids constituting a certain protein are specific to the protein and cannot be changed. Accordingly, among the essential amino acids, the one(s) in least supply control the amount of protein(s) produced by the animal. When essential amino acids are lacking in the ruminant diet the ruminant's health, milk production, etc. are all negatively affected.

Since increasing the milk production of lactating dairy cattle is an ongoing challenge facing the dairy industry, many attempts have been made to provide a method for doing so. For example, Smith et al (U.S. Pat. No. 5,145,695) provide a method wherein a particular feed composition which delivers an improved balance of essential amino acids post-ruminally is fed to a cow. Nissen (U.S. Pat. No. 4,758,593) discloses a method wherein lactating domestic mammals are fed ketoisocaproate to improve the quantity and quality of milk produced. Kantor (U.S. Pat. No. 4,704,276) provides a method wherein lactating ruminant animals are fed certain antibiotics in order to increase lactation. Palmquist et al (U.S. Pat. No. 4,642,317) discloses a process of feeding ruminant animals increased amounts of fat while they are lactating in order to increase milk yield. Similarly, Mantha (U.S. Pat No. 4,175,121) discloses a process wherein essential nutrients, a methionine hydroxy analog, minerals, vitamins, proteins, Aspergillus oryzae and a buffer are fed to lactating cows to improve overall milk production. Rawlings et al (U.S. Pat. No. 4,225,620) describe a method wherein an alkali treated proteinaceous feed supplement is fed to ruminant animals so as to promote milk production. Finally, Cummins (U.S. Pat. No. 4,388,327) describes a process wherein the weight of milk produced by dairy cattle can be increased by supplementing the diets of cattle with γ-methylmercapto-α-hydroxybutyric acid and its oligomers starting two weeks prior to the scheduled date of calving and for 112 days of production. All of the references described above are incorporated herein by reference.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide a method for supplementing amino acid levels in ruminant animals by feeding said animals a rumen-protected amino acid-supplemented feed.

Another object of the present invention is to increase and maintain the health of ruminant animals by feeding said animals a diet supplemented with rumen-protected amino acids.

Another object of the present invention is to increase a ruminant's milk production by feeding said ruminant animal a base feed which has been supplemented with rumen-protected lysine and/or rumen-protected methionine.

Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following summary and detailed description of the invention.

SUMMARY OF THE INVENTION

The present invention is based upon the discovery that the health, appetite, quantity and quality of milk, etc., in ruminant animals can be improved by administering a rumen-protected feed additive comprising lysine and, optionally, methionine thereto. Such administration may begin at any time: for example 60, 30, 10 or 5 days prior to calving or 1, 10, 20 or 29 days after calving and may stop, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 250 or 305 days or one month, two months, three months, four months or five months into the lactation period, with a minimum administration time of 2 days. A preferred feeding period is the period beginning in the ruminant's late gestation period (approximately 3 weeks prior to the scheduled parturition date) and continuing for 30, 70, 90, 120, 150, 160 or 305 days into the ruminant's lactation period. Particularly preferred feeding periods start at about 3 weeks pre-calving and end about 70 days or about 5 months post-calving, where "about" means up to ±8 days. While a ruminant's cycle includes a dry period, feeding in the dry period is not necessary except for the preferred times pre-calving.

While improving the milk production of dairy cattle, particularly high-producing dairy cattle, is an important commercial application of the present invention, it can also be advantageously used with all other female ruminants that produce milk such as sheep, water buffalo and goats.

The present invention is preferably practiced by combining a rumen-protected lysine and/or methionine composition with a standard animal feed wherein a lysine and/or methionine core composition is protected with a coating of lecithin, at least one inorganic substance which is stable in neutrality and soluble under acidic conditions, and at least one substance selected from saturated or unsaturated monocarboxylic C₁₄₋ C₂₂ acids, salts thereof, hardened vegetable oils, hardened animal oils, and waxes, wherein the methionine source to lysine source weight ratio in the core, when methionine is present, is from 1/10 to 10/1, preferably 1/3. It is also preferably practiced with a rumen-protected lysine/methionine composition wherein the core is coated with substances including a polymer as described in U.S. Pat. No. 4,996,067 and U.S. Pat. No. 4,937,083, both incorporated herein by reference.

The present invention is also practiced by feeding said ruminants (a) a low protein feed each day beginning approximately 6 weeks prior to the scheduled parturition date of said ruminant animal, (b) a feed which has protein content between low and middle protein, together with, or without, a rumen-protected feed additive comprising lysine, methionine or a mixture thereof each day beginning between approximately 4 weeks and approximately 1 week prior to said scheduled parturition date, (c) a middle protein feed together with said rumen-protected feed additive each day beginning on the parturition day of said ruminant for a period of between approximately 4 weeks and approximately 5 months, and (d) a middle protein or high protein feed each day during the remaining lactation period of said animal.

While it is known that lactating cows are fed protein in successively increasing amounts as lactation proceeds (see Example 5, Control treatment), the benefits obtained via concurrent use of a rumen-protected amino acid (RPAA) for a certain period during the gestation and/or lactation period is part of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents the milk production over time from cows used in Example 4.

FIG. 2 represents the fat-corrected milk over time from cows used in Example 4.

FIG. 3 represents the fat production over time from cows used in Example 4.

FIG. 4 represents the protein percent over time from cows used in Example 4.

FIG. 5 represents the protein production over time from cows used in Example 4.

FIG. 6 represents the solids-corrected milk production over time from cows used in Example 4.

FIG. 7 represents the Wood curves of the control group cows used in Example 6.

FIG. 8 represents the Wood curves of the experimental group cows used in Example 6.

DETAILED DESCRIPTION

The feed additive of the present invention comprises a rumen-protected amino acid (RPAA) additive comprising a core of lysine and/or methionine, which additive has been protected from digestion in the rumen of ruminant animals by a coating. Any rumen-protective coating may be used to keep the lysine and methionine from being digested in the rumen. A preferred protective coating comprises lecithin, at least one inorganic substance which is stable in neutrality and soluble under acidic conditions, and at least one substance selected from straight- or branched-chain saturated or unsaturated C₁₄₋ C₂₂ monocarboxylic acids, salts thereof, hardened vegetable oils, hardened animal oils, and waxes. This material is prepared as described in U.S. Pat. No. 5,277,166 (incorporated herein by reference) and provided as particles of from 0.1-30 mm in diameter, preferably 1-3 mm, with a specific gravity of 1.1-1.8, preferably 1.2-1.3. The particle size and specific gravity of the RPAA additive may be adjusted to preferably provide a residence time of between 10 and 14 hours for the RPAA in the rumen of the animal, preferably 12 hours, before proceeding to the lower stomachs for digestion/absorption.

In another embodiment, the present invention relates to the use of a RPAA feed additive as described above, wherein the lecithin is present in an amount of from 0.1% to 20% by weight and the inorganic substance is used in an amount from 0.1 to 10% by weight, based on the weight of the coating composition. In yet another embodiment, the present invention relates to the RPAA feed additive described above wherein the inorganic substance is calcium or magnesium carbonate, a calcium salt of pyrophosphoric acid or talc (magnesium silicate hydroxide).

The lecithin used in the RPAA coating is not required to be pure. A mixture of phosphatidyl choline, phosphatidyl ethanolamine and phosphatidyl inositol may be used. Preferably, it may be prepared from soybean and egg yolk.

Examples of the inorganic substance which are stable under neutral conditions and soluble under acidic conditions include magnesium carbonate, calcium carbonate, calcium phosphate, calcium pyrophosphate and mixtures thereof. Carbonates such as magnesium carbonate, calcium carbonate and the calcium salt of pyrophosphoric acid are preferred.

Examples of suitable monocarboxylic acids useful in the above-described preferred coating composition include myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, and behenic acid. Salts of these may also be used. Examples of hardened vegetable oils include hardened palm oil, hardened soybean oil, hardened rapeseed oil, and hardened castor oil. Examples of hardened animal oils are hardened beef tallow and hog fat. Examples of waxes are carnauba wax and beeswax, natural waxes, synthetic waxes, and paraffin waxes.

The preferred coating composition described above is such that, on the basis of all coating materials, it comprises 0.1 to 20% by weight of lecithin, 0.1 to 10% by weight of the inorganic substance which is stable under neutral conditions and soluble under acidic conditions, preferably 1 to 10% of lecithin and 1 to 10% of the inorganic substance. If the amount of lecithin in the coating materials exceeds 20% by weight, the strength of the coating layer is decreased and the protectiveness in the rumen is reduced. If the amount of lecithin is less than 0.1% by weight, the emulsification action is insufficient, and the dissolving action in the abomasum and subsequent digestive tract decreases. If the amount of the inorganic substance which is stable under neutral conditions and soluble under acidic conditions exceeds 10% by weight, the protectiveness in the rumen decreases. If it is below 0.1% by weight, the action of the inorganic substance inside of the abomasum is insufficient.

Other preferred coating compositions useful in the present invention include the one described in U.S. Pat. No. 4,966,067, directed to a feed additive for ruminants which comprises cores containing an acid salt of a basic amino acid, and a first coating layer and a second coating layer coated sequentially on the surface of each core, wherein said first coating layer contains at least one first coating agent selected from the group consisting of a neutral or weakly acidic organic substance, a substantially neutral fine powder of inorganic substance, a non-ionic hydrophilic polymer substance and an anionic hydrophilic polymer substance and being physiologically acceptable to the ruminants, and the second coating layer contains as a second coating agent a polymer soluble or swellable in water in an acidic region of a pH of at most 5.5. Another coating composition suitable for use in the present invention is the one described in U.S. Pat. No. 4,937,083, directed to a core containing a carbamate of a basic amino acid and coated with a polymer coating agent soluble or swellable in water in an acidic region of a pH of at most 5. Both U.S. Pat. Nos. 4,966,067 and 4,937,083 are incorporated herein by reference, wherein the coatings and cores described therein contain the lysine and/or methionine necessary to supplement ruminant feed according to the present invention.

There is no particular restriction in the preparative method of the core containing methionine and/or lysine which is later coated. As required, a binder or a filler may be added to the amino acid(s) and granules, preferably granules close to spherical in shape, are prepared by a known granulating method such as extrusion granulation, fluidized granulation, or stirring granulation. Examples of the binder are cellulose derivatives such as hydroxypropylcellulose, methyl cellulose, or sodium carboxymethylcellulose, vinyl derivatives such as polyvinyl alcohol or polyvinylpyrrolidone, gum arabic, guaiac gum and sodium polyacrylate. Starch, proteins and crystalline cellulose may be used as the filler. If required, one or more specific gravity adjusting agents may be added such as calcium carbonate, calcium phosphonate or talc. These cores may be rumen-protected in any effective manner known in the art.

The amount of the coating materials used to coat the core substance(s) is not restricted in any particular manner. The amount should be as little as possible for economic reasons, but should be enough to fully protect the lysine and/or methionine in the rumen. Usually the amino acid cores are coated in an amount of 10 to 200 parts by weight, preferably 15 to 150 parts by weight, per 100 parts by weight of the cores containing the amino acids. Any other coating system other than the preferred one described above may be used to protect the lysine and methionine core from digestion in the rumen, such as the acid-sensitive polymers described in U.S. Pat. No. 4,937,083, the fatty acids described in U.S. Pat. No. 3,959,493, the coating composition of U.S. Pat. No. 4,837,004 and the coating described in U.S. Pat. No. 4,842,863, all of which are incorporated herein by reference. There is no particular restriction on the method of coating the lysine and/or methionine core either. It can be coated by an ordinary method such as fluidized-bed coating, pan coating or melt coating.

The lysine used to prepare the core of the RPAA feed additive may be L-lysine or D,L-lysine and the methionine used to prepare the core of the RPAA feed additive may be L-methionine or D,L-methionine. Other methionine sources such as glycyl-D,L-methionine etc. (see U.S. Pat. No. 3,959,519, incorporated herein by reference) may be used in place of pure methionine, as well as the ruminant-acceptable acid addition salts of both lysine and methionine such as the HCl salts. The coated feed additive core may contain lysine, methionine or both in its core.

The lysine/methionine RPAA coated feed additive described above is mixed with a base feed commonly fed to domestic ruminant animals in an amount sufficient to supplement the metabolizable protein present in the base feed to a level sufficient to maintain the health, increase the milk production, etc., of the particular ruminant being fed, in view of its weight, lactation, desired milk composition, rate of weight loss or gain, etc. The rumen-protected lysine/methionine feed additive should preferably be uniformly distributed throughout the feed. If both lysine and methionine are needed, they may each be separately added to the feed as single-component RPAAs or an RPAA containing both lysine and methionine in the desired ratio in its core may be added. Typical dry feed components to be supplemented according to the present invention include mixtures of grass, legume, corn or small grain silage, legume, grass or small grain hay, grain by-products, small grains, oil seeds and oil seed meals like corn grain, eared corn, shelled corn, barley, sorghum grain, soybean meal, cotton seed, corn gluten meal, corn silage, grass silage, alfalfa hay, prairie hay, etc. After mixing a rumen-protected amino acid methionine/lysine feed additive with the dry feed, the feed material may be further processed, such as by conversion to pellets, etc.

The amount of RPAA feed additive added to a base feed depends upon a number of factors and is calculated as the difference between the animal's amino acid requirement and the amount of amino acids supplied by the animals' feed plus the amount in the animal's reserve. In general, the amount added of RPAA is the amount necessary to meet requirements for growth, maintenance, productivity and health. This amount may be based upon, e.g., common experience, academic research, etc.

For example, Heinbeck has developed a modeling system for formulating dairy rations on an amino acid basis (Degusa Technical Symposium, Saskatoon, Saskatchewan, Canada, Sep. 12, 1989, incorporated herein by reference). The model is divided into two parts: one part relates to the calculation of the amount of amino acids required for an animal's maintenance and production and the other part relates to the calculation of the amount of amino acids provided by feedstuffs.

In Heinbeck's system, the metabolizable amino acid requirement is calculated from the milk production and the maintenance requirements of the animal. The amino acid requirement for milk production is calculated based upon the amount of milk produced, its crude protein content, the amino acid content in the crude milk protein and the efficacy of metabolism. For example, according to the model a ruminant's methionine requirement based upon its milk production may be calculated as follows: for a ruminant producing 40 kilograms per day of milk containing 3.5% by weight of crude protein, said crude protein containing 2.6% by weight methionine, the net amount of methionine necessary for lactation is 40,000 g×3.5%×2.6%=36.4 g. The efficacy of metabolism of methionine is 70%; thus the amount of methionine necessary for this particular ruminant's lactation is 36.4 g/0.7=52 g. This required amount of methionine is added to the amount of methionine the ruminant requires for maintenance, which is estimated from literature crude protein requirements and the amino acid composition of meat to be approximately 7 grams. Thus, the methionine requirement for a ruminant producing 40 kilograms of milk per day having 3.5% crude protein is 59 grams per day (the summation of the methionine requirement for milk production and maintenance).

The amount of amino acids delivered by feedstuffs according to the model may be calculated by summing the amino acid content of the feed ingredients, said amino acid content being known in the literature and/or calculatable by, e.g., amino acid analysis. This feedstuff amino acid is reduced by the efficacy of metabolism, etc. and added to the amount of amino acids delivered which are derived from the microbial crude protein metabolized by the ruminant to provide the total amount of amino acids the ruminant receives. For example, the amount of rumen bypassed methionine (the amount of methionine which passes the rumen and is metabolized by the ruminant) calculated for the following feed for the above-described ruminant (including microbial protein) was 52.5 grams.

    ______________________________________     ALFALFA HAYLAGE                    17.6     (crude protein content %)     GRASS HAY      16       (crude protein content %)     HM CORN        9.56     (crude protein content %)     CONCENTRATE    36.4     (crude protein content %)     ______________________________________

See Livestock Feeds and Feeding, Church, D. C. Prentice Hall, N.J., 1991, incorporated herein by reference, for the method of measuring crude protein, particularly page 34, thereof.

Accordingly, since the feedstuff described above provides 6.5 g/day of methionine less than required (89% of daily requirement), the above-described feed, according to the present invention, would be supplemented by the RPAA to provide this 6.5 g/day of rumen-stable methionine. The amount of lysine required, the amount of lysine supplied by the feed, and the amount of lysine needed to supplement the feed is calculated in the same way.

Another method available for calculating ruminant requirements and feedstuff supply is the Cornell Net Carbohydrate and Protein System for Evaluating Cattle Diets (Search: Agriculture. Ithaca, N.Y.: Cornell Univ. Agr. Exp. Sta. No. 34, 128 pp. 1990, ISSN 0362-2754, incorporated herein by reference) which provides a model for predicting cattle requirements and feedstuff utilization designed to be used for adjusting cattle nutrient requirements and calculating utilization over wide variations in breed, feed, management, environmental conditions, etc. The model is available on a computer spread sheet and may be applied to both beef and dairy cattle at different levels and types of production. The Cornell model allows one to calculate the metabolizable protein for, e.g., dairy cattle based upon their breed, weight at birth, gross weight, etc., in view of the particular circumstances of the individual cow (i.e., whether the cow is simply in a maintenance cycle, a lactation cycle, a weight-gain period, etc). The model also provides animal responses to given diets based upon feed composition, digestion rates, digestible protein (based upon both digestible feed and digested bacterial protein which has escaped from the rumen), etc. The metabolizable protein required by a particular ruminant is thus calculated and may be compared with the calculated amount of metabolizable protein provided by a given feed. When the feed provides a lower amount of metabolizable protein than is required by a particular cow based upon its physical condition, lactation stage, etc., the feed is then supplemented by the RPAA feed additive described above to the required level.

The amount of RPAA feed additive added to the base feed is calculated by converting the amount of metabolizable protein lacking in the diet into the amount of ruminally-protected methionine and/or lysine necessary to make up for this deficiency. This conversion may be accomplished by, for example, conducting an amino acid analysis of the digestible protein supplied by a feed by first separating the protein fractions of the feed into rumen-degraded and rumen degradation-resistant fractions according to the method described in Chlupa et al (1991 Cornell Nutrition Conference for Feed Manufacturers, p. 44, incorporated herein by reference) or by the method described in the Cornell Net Carbohydrate and Protein System described above. In the alternative, the amount of methionine and lysine a particular ruminant requires may be calculated by summing the amount of methionine and lysine required for lactation and maintenance calculated by the Cornell model.

For example, a ruminant producing 88 pounds per day of milk containing 3.05% crude protein needs 88 lb×453.6 g/lb×3.05%=1220 g/day of crude protein to replenish the amount given daily in the milk. The percentage of lysine and methionine in the crude milk can be analyzed and multiplied by the amount of crude protein necessary for lactation to provide the minimum lysine and methionine requirement for lactation. This number is then adjusted for the efficiency with which the ruminant metabolizes its intake methionine and lysine. For example, for milk having crude protein which is 2.7% methionine and 8.3% lysine, and knowing that the efficiency of digestible methionine and lysine for the ruminant is 75%, the amount of methionine necessary to satisfy the ruminant's lactational requirements is (1220 g/day×0.027)÷0.75=43.9 g. The amount of lysine may be similarly calculated to be 135.0 g. Of course, the ruminant must also maintain itself, and it requires protein to do so. This maintenance requirement may be calculated based upon the Cornell model described above as the summation of the scarf, urine and feces protein required for the particular ruminant. The scarf and urine protein requirements are then multiplied by 0.027 and the feces requirement by 0.028 to determine the methionine requirement and all are multiplied by 0.083 to determine the lysine requirement. In order to fully calculate the metabolizable protein required the Cornell fecal protein requirement is added to the above scarf, urine and feces requirement to provide a total amount of protein required which is again multiplied by 0.028 (methionine) or 0.082 (lysine) to determine the total amount of methionine and lysine required.

The metabolizable amino acid supplied to the ruminant may also be calculated according to the Cornell method and includes summing the amount of lysine and methionine which comes from the digested bacterial protein with that which comes from the feed and which bypasses the rumen. The Cornell method provides the total bacterial protein a ruminant receives in the lower stomach, and this total may be converted to methionine and lysine by multiplying by the factors of 0.028 and 0.082, respectively. Similarly, the Cornell model provides the total amount of rumen bypass protein originating from feed based upon the particular composition of a feed, and the amount of methionine and lysine delivered may be calculated based upon the amount of methionine and lysine contained in the digestible protein fractions of each particular feed component.

The lysine and methionine requirement can be calculated by summing the lactational requirement and metabolyzable requirement. The lactational requirement is calculated from the amount of milk produced per day and the amount of each amino acid in the milk, correcting for the ruminant's efficiency of conversion of the amino acid to milk protein (75% for lys and met). The metabolyzable requirement ins mentioned above and contains scarf, urine and fecal requirements, etc.

In this way it is clear how much rumen-protected lysine and rumen-protected methionine may be added to a base feed which is fed to ruminants according to the present invention. Of course, lesser and excess amounts may be added, as desired.

Once the RPAA supplemented feed has been prepared, it is fed to ruminant animals. Several administration periods are effective. One period begins just prior to the onset of lactation (calculated from breeding records; usually approximately 3 weeks (approximately 21 days) prior to parturition) and extends between 1 day and 5 months into the animal's lactation period. Another effective period begins just after calving, or about 28 or 29 days after calving and stops between 100 and 150 days into the lactation period. Other possible start and end dates were described above. The amount of methionine/lysine RPAA-supplemented feed fed to the ruminant animals during this period should range between 3.0 to 5.0 percent of the animal's body weight, i.e., about 40-80 pounds of 100% dry material per day for an average dairy cow.

The present inventors have also discovered that L-sysine and DL-methionine in various other rumen-protected forms also provide the "residue effect". This fact is demonstrated in Example 6 below where cores of L-lysine and/or DL-methionine are coated with a rumen-protective coating. Particularly preferred forms of rumen-protected amino acids useful herein for obtaining the "residue effect" include L-lysine and/or DL-methionine dispersed in a matrix composed of a coating substance for the coated form such as, e.g., hardened beef tallow and a binding material such as, e.g., CMC (carboxymethylcellulouse), xanthan gum, starch, sugars, carragheenin, etc. Such dispersed forms are known in the art and are described in, e.g., U.S. Pat. No. 4,842,863 and U.S. Pat. No. 3,562,806, both of which are incorporated herein by reference in their entirety.

Having generally described -his invention, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only and are not intended to be limiting.

EXAMPLES

Examples 1 and 2: Preparation of rumen-protected amino acid (RPAA) feed additive:

Example 1

A kneader was charged with 325 g of L-lysine hydrochloride, 172.5 g of talc, 2.5 g of sodium carboxymethylcellulose and 1345 g of water. They were kneaded and then by using an extruder having a screen with an opening size of 1.5 mm, a cylindrical granule was obtained. The granule obtained was molded by using a spherical granule producing machine ("Marumerizer", Fuji Paudal Co., Ltd.) to obtain a granule similar to a spherical shape. The resulting spherical granule was dried by fluidized-bed dryer to obtain a core containing L-lysine hydrochloride.

5 parts by weight of lecithin (soybean lecithin, manufactured by WAKO pure chemical industries, ltd.--food additive--was used) and 5 parts by weight of magnesium carbonate was dispersed in 90 parts by weight of melted hardened beef tallow. This coating material was coated on the L-lysine hydrochloride core in an amount of 67 parts by weight per 100 parts of the core (the rate of coating 40%). A fluidized-bed coater ("New Marumeizer", Fuji Paudal Co., Ltd.) was used.

Example 2

The preparation of a RPAA feed additive was conducted in the same manner as in Example 1 except that calcium carbonate was used instead of magnesium carbonate.

Example 3

A RPAA according to U.S. Pat. No. 4,996,067 was prepared as follows:

(a) Granulation of the core material

Into a centrifugal fluidized granulation coating apparatus (CF-360, Freund Sangyo K.K.), 180 g of crystals of L-lysine hydrochloride having a particle size of from 20 to 24 mesh were charged as seed cores, and granulation was conducted by gradually adding 2,200 g of a 10:1 mixture of L-lysine hydrochloride and fine crystalline cellulose (disintegrator) under rotation while spraying 1,630 g of a 4% aqueous solution of hydroxypropyl cellulose as a binder. The granules thus obtained were dried in a fluidized bed dryer until the water content became less than 1% by weight and classified, by means of a standard sieve to obtain granules of from 10 to 12 mesh containing 89.5% of L-lysine hydrochloride.

The content of the amino acid in the particles was obtained by dissolving 1 g of the sample in 200 ml of the Clark Lubs buffer solution and quantitatively analyzing the content by high performance liquid chromatography.

(b) First coating

2,000 g of the granules of L-lysine hydrochloride obtained in the above step (a) were charged into a centrifugal fluidized granulation coating apparatus, and coating treatment was conducted by supplying 880 g of a fine powder of D,L-methionine as the first coating agent under rotation, while spraying 1,000 g of a 4% aqueous solution of hydroxypropyl cellulose as a binder, followed by drying in a fluidized bed dryer, to obtain a first coating product having a particle size of from 9 to 10 mesh coated with D,L-methionine containing 64.5 of L-lysine hydrochloride, 25.8% of D,L-methionine and 9.7% of cellulose+hydroxypropyl cellulose.

Among the components in the particles, amino acids were quantitatively analyzed by the method as described in the step (a). The amounts of other components were obtained by subtracting the amounts of amino acids from the weight of the particles.

(c) Second coating

A mixture comprising a copolymer (reduced viscosity at a concentration of 0.5 g/dl in ethanol: η_(sp/c) =1.30) of 70% of 4-vinylpyridine with 30% of styrene and stearic acid (fusion-preventing agent) in a 1/6 amount of the copolymer, was dissolved in ethanol to obtain an ethanol solution having a concentration of 4%. This ethanol solution was sprayed from a nozzle, and at the same time, talc was gradually continuously supplied in small portions in the form of a powder. The solution and the talc powder (fusion preventing agent) were supplied in such amounts that the weight ratio of the copolymer:talc powder:stearic acid would be 30:65:5 and used as the second coating agent.

600 g of the first coating product obtained in the above step (b) was supplied to a fluidized coating apparatus and a second coating layer was formed thereon by means of 2,060 g of the ethanol solution of the copolymer and stearic acid and 192 g of talc powder. After coating, the coated product was dried at 70° C. for 5 hours to obtain 833 g of a second coating product. The proportion of the second coating layer in the entire particles, was 28%.

The specific gravity (as measured by an air comparative type specific gravity meter, the same applies in the subsequent Examples) of the particles of the second coating product thus obtained was 1.10.

The coating apparatus is connected with a suction duct for waste gas, whereby the polymer solution sprayed in the coating apparatus and the fine solid particles added during the formation of the first coating layer or the second coating layer, are effectively used, and the proportion of the materials deposited is usually from 70 to 90%, although it varies depending upon the operational conditions.

The feed additive thus obtained was subjected to shaking in the McDougall buffer solution at 39° C. for 24 hours, whereupon L-lysine hydrochloride and D,L-methionine in the feed additive were found to be maintained in a total amount of 97%. Further, when shaked in the Clark Lubs buffer solution at 39° C. for 2 hours, L-lysine hydrochloride and D,L-methionine eluted in a total amount of 95%, and when shaked for 3 hours, they eluted 100%,

Example 4

Multiparous, lactating Holstein dairy cows (10 cows per treatment) were used to evaluate the efficacy of being fed a rumen-protected amino acid (RPAA) described above for a certain period of time. For the first 28 days postpartum, all cows received a Negative-control (NEG) diet of alfalfa hay (2.5 kg DM/d), timothy hay (2.4 kg DM/day) and corn silage (ad libitum). Concentrate (corn, soybean meal (SBM), corn gluten meal; 18.6% crude protein) and soybean meal were fed according to production (0.35 kg concentrate/kg milk; 0.1 kg SBM/kg milk above 35 kg/d). This period is known as the standardization period and can be 2 weeks, 21 days or 28 days. See Polan et al, J. Dairy Sci, Vol 74, No. 9, 1991, p. 2997, and R. Erdman et al, J. Dairy Sci., Vol. 74, No. 5, 1991, p. 1641, both incorporated herein by reference. From 29 days postpartum, RPAA-supplemented cows received lysine-HCl (19 g/d) and methionine (6.5 g/d) encapsulated in a ruminally inert coating, until 150 d (RP150) or 305 d (RPAA) postpartum. Positive-control (POS) cows received an additional topdress of SBM and bloodmeal (0.4 kg/d). Compared to NEG cows, POS and RPAA cows produced more (P<0.05) milk (32.5, 34.0 and 34.7 kg/d respectively) from 29 to 150 d postpartum. Milk fat content from NEG cows was similar to POS cows, but lower (P<0.06) than for RPAA cows (3.41, 3.48 and 3.59% respectively). Milk protein content was similar among treatment groups. From 29 to 305 d postpartum, POS and RPAA-supplemented cows produced more (P<0.05) milk than NEG cows (25.9, 27.5, 28.8 and 29.7 kg/d for NEG, POS, RP150 and RPAA cows respectively), but milk composition was unaffected by treatment. The RPAA was effective in increasing milk production, and this positive effect continued after RPAA was removed from the diet.

Experimental Animals

Forty multiparious Holstein cows were used in a full lactation study. Animals were assigned to experimental treatment groups as they freshened and blocked within groups by age. The blocks were for cows entering their second lactation; third to first lactation; and sixth or greater lactation.

Experimental Diets

All cows were fed a common diet, consisting of corn silage, corn and timothy hay, for at least two weeks pre-calving. At parturition, all cows received the negative control diet (described below) until 28 days in milk production period. On Day 29, cows were assigned to one of four treatment groups designated as negative control (NEG), positive control (POS), negative control diet plus RPAA supplementation until Day 305 of lactation (RPAA), and negative control diet plus RPAA supplementation until Day 150 of lactation (RP150).

The NEG diet was designed to meet National Research Council (1989) recommendations for undegradable intake protein (UIP), but was deficient in methionine and lysine, as predicted by the Cornell Net Carbohydrate-Protein Model (Fox et al 1990) described above. The RPAA and RP150 diets were identical to the NEG diet except that cows were offered 0.5 kg concentrate containing 50 g rumen-protected amino acids (17 g lysine-HCl; 6.5 g D,L-methionine). Cows receiving the POS diet were fed similarly to the other diets except that an additional 400 g soybean meal-blood meal topdress. This was sufficient to provide the same level of rumen-degradable methionine and lysine as RPAA-supplemented cows.

All animals were offered, daily, corn silage ad libitum, 4 kg alfalfa hay and 4 kg timothy hay. Concentrate (Table 1) was fed according to production (1 kg concentrate per 2.5 kg milk production). A soybean meal-blood meal topdress was fed to cows according to level of milk production. Amount of concentrate and topdress was adjusted weekly for each cow. Sufficient corn silage was offered to allow for a 10% weighback of total diet. Feed refusals were weighed once per day and separated into hay and non-hay fractions. These fractions were subsampled once per week and a composite sample was used for chemical analyses.

Data Collection

Animals were weighed and scored for body condition on entry to their respective treatment groups and on a monthly basis thereafter. Milk production was recorded on a daily basis. Milk samples were collected once per week from the AM and PM milkings from each cow and submitted for compositional analysis (milk protein, fat, lactose and somatic cell count).

Corn silage was sampled weekly and all other feedstuffs were subsampled weekly and subjected to proximate analysis (crude protein, ADF, NDF, Ca, P, and DM) as described by Beauchimin et al (1991) J. Dairy Sci. 74: 3128-3139 (incorporated herein by reference). Analyses of protein fractions was accomplished by art-accepted methods.

                                      TABLE 1     __________________________________________________________________________     Composition of feedstuffs fed to lactating cows with or without RPAA.                                 corn            alfalfa                timothy                    corn                       corn                          soybean                              beet                                 gluten                                     blood                                        con-            hay hay silage                       grain                          meal                              pulp                                 meal                                     meal                                        centrate     __________________________________________________________________________     Dry matter, %            92.1                92.5                    33.8                       93.7                          91.8                              92.7                                 94.1                                     93.1                                        91.5            % of DM     ND fiber            40.7                59.3                    50.3                       22.4                          12.8                              50.5                                 17.0                                     99.2                                        28.4     AD fiber            30.3                40.6                    29.1                       4.5                          6.5 27.0                                 7.4 7.1                                        8.1     N × 6.25            20.7                12.3                    9.5                       11.5                          55.2                              11.0                                 60.3                                     81.3                                        38.6     Calcium            1.51                1.06                    0.35                       0.02                          0.26                              0.47                                 0.15                                     0.06                                        0.22     Phosphorus            0.26                0.22                    0.22                       0.24                          0.78                              0.09                                 0.45                                     0.07                                        0.38            % of total N     buffer sol. N            45.2                43.6                    36.0                       18.7                          21.0                              32.9                                 13.5                                     7.1                                        17.6     ND soluble            79.6                74.2                    89.7                       98.4                          90.2                              78.8                                 94.5                                     16.5                                        89.5     __________________________________________________________________________      ND fiber = neutral detergent fiber      AD fiber = acid detergent fiber      N = nitrogen

Statistical Analyses

Data analysis consisted of using repeated measures analysis on weekly milk yields, with a covariate period. The covariate value was obtained from the average milk or milk component production during Days 15 through 28 post-partum. Treatment groups RPAA and RP150 were combined as one treatment (RPAA) until 150 days post-partum. Linear contrasts were used for means separations between treatment groups. Blocks consisted of the groups of four animals, within lactation groups, that were formed as cows entered the experiment. The General Linear Model (GLM) of SAS (1990) was used For analyses of variance. Linear contrasts were used to test for treatment differences. The contrasts were RPAA vs. POS, RPAA vs. NEG, and RPAA vs. RP150 (for Days 150 to 305 postcalving). Milk yield, milk component and milk component yields were analyzed using their respective covariate measurements.

Body weight and body condition score (BCS) were statistically analyzed, except that monthly measurements were used and post-calving values served as the covariate. Feed intake and blood parameters were analyzed, using weekly averages but no covariate value was used.

RESULTS

Composition of ingredient feedstuffs fed to cows in this study (Table 1) were typical of similar feeds reported elsewhere (see the Cornell Model described above). The exception to this was the blood meal which contained >90% of the nitrogen (N) as NDF-N. This unusually high value may be due to analytical problems encountered in filtering this feedstuff. However, identical results were observed for the blood meal when analyzed by two separate laboratories. If the observed value for blood meal was not an analytical aberration, then the undegradable intake protein (UIP) of the Positive-control diet may have been greater than originally planned.

DRY MATTER intake

Dry matter (DM) intake, expressed in kg per day, was similar among all treatment groups, although there was a small numerical advantage for RPAA cows during the first 150 days postpartum. However, when DM intake is expressed per unit body weight, RPAA cows consumed more DM during the first 150 days (P<0.063) and over the entire lactation (P<0.079) than NEG cows. Conversely, POS cows consumed less DM than NEG cows.

The greatest dry matter intake for RPAA cows occurred, for the most part, during 12 to 20 weeks postcalving (8 to 16 weeks post-treatment). This corresponded with the interval of highest milk production and subsequent greatest access to concentrate. This was also the time when the body weights for RPAA cows were the lowest (mainly due to the RP150 subgroup). Conversely, POS cows did not readily accept blood meal, which may account for the lower DM consumption per unit body weight observed, as compared to NEG cows.

Milk production

Cows on the RPAA and POS treatments produced significantly more milk and fat-corrected milk (FCM) than NEG cows (FIGS. 1 and 2). Peak milk production was similar for all treatment groups, but persistency of NEG cows was lower than for other treatment groups. However, peak FCM yield was greater for RPAA and POS cows than NEG cows. Cows supplemented with RPAA were able to maintain this peak production longer than POS cows.

At 150 days postcalving (17 weeks post-treatment), RPAA was removed from the diets of RP150 cows. Milk and FCM production for RP150 cows began to decline numerically within a week. By Weeks 23 and 21, RP150 cows were producing significantly (P<0.05) less than RPAA cows for milk and FCM respectively. The production for RP150 cows declined to the level of the POS cows until the end of lactation. Despite the fact that RP150 cows were receiving the same diet as the NEG cows (no supplemental RPAA), the production level was equal to the POS cows, indicating a residual response to the RPAA after withdrawal of the supplement.

Fat production (FIG. 3) declined for all groups as lactation progressed. The decline was most severe for NEG cows. This would be indicative of cows deficient in energy reserves. However, the decline in body condition score was less severe for NEG cows than for other treatments. Later in lactation, POS cows were significantly lower (P<0.05) in milk fat percentage an other groups. This may have been due to the lower body reserves and relatively high milk production compared to NEG cows. This was not the case for RPAA cows, even though milk production was numerically greater for RPAA compared to POS cows. This could be attributable to the additional energy needed by POS cows to excrete extra nitrogen in the urine, or a beneficial effect of RPAA supplementation to maintaining milk fat percentage despite losses in body condition.

Overall, RPAA cows produced more fat (kg/d) and had a higher milk fat percentage than NEG cows. There was a trend toward higher fat production for RPAA compared to RP150 cows. This difference was primarily due to differences in milk yield. Similarly, POS cows produced more milk Cat than NEG cows, which was related to milk volume rather than fat percentage.

Milk protein production was greater for RPAA and POS cows compared to NEG cows (Table 2). However the level of significance was greater for the RPAA compared to protein supplementation (P<0.001 and 0.062 respectively). There was a trend toward more milk protein production when RPAA was fed for the entire lactation compared to Day 150. This difference Is attributable to differences in milk volume and to the decrease in milk protein content in RP150 cows, observed when RPAA was withdrawn from the diet (FIG. 4).

The positive response in protein production was observed within two weeks of RPAA supplementation whereas with protein supplementation, it was nine weeks before protein production was greater than for unsupplemented cows (FIG. 5). No differences were observed in milk protein content over the entire experiment. However, milk protein content was greater for RPAA cows compared

                  TABLE 2     ______________________________________     Mean (covariate adjusted) milk protein production and milk protein     percentage for groups of cows, supplemented with or without     ______________________________________     RPAA.     kg/d                   % of Neg-control     Days of lactation          Days of lactation     29-150       29-305   SEM.sup.2                                    29-150 29-305     ______________________________________     Protein production     Neg-control             1.009    0.853    --     --     --     Pos-control             1.060    0.908    --     105.0  106.4     RP150   --       0.928    --     --     108.8     RPAA    1.098    0.955    --     108.8  112.0     Significance     N vs P.sup.3              .071     .062    .011     N vs R.sup.4              .006    <.001    .009     R vs R150.sup.5             --        .164    .012     ______________________________________     %                      % of Neg-control     Days of lactation          Days of lactation     29-150       29-305   SEM      29-150 29-305     ______________________________________     Protein percentage     Neg-control             3.12     3.34     --     --     --     Pos-control             3.13     3.29     --     100.2   98.5     RP150   --       3.29     --     --      98.6     RPAA    3.17     3.30     --     101.6   99.0     Significance     N vs P  NS       NS       .061     N vs R  NS       NS       .048     R vs R150             --       NS       .045     ______________________________________      .sup.1 Covariate period consisted of Days 14 through 28 of lactation.      .sup.2 Standard error of the mean.      .sup.3 Linear contrast of Negativecontrol vs. Positivecontrol treatment      groups.      .sup.4 Linear contrast of Negativecontrol vs. RPAA treatment groups.      .sup.5 Linear contrast of RPAA vs. RP150 treatment groups.

to NEG cows in early lactation, but the reverse occurred in late lactation. The positive response in milk protein content, to RPAA supplementation, occurred within one week of RPAA supplementation.

Production of solids-corrected-milk (SCM) showed similar results to production of milk volume (FIG. 6).

Example 5

Thirty multiparious (i.e., 2-7-parious) Holstein cows (10 cows/treatment) were used to evaluate the efficacy of being fed a rumen-protected amino acid (RPAA) for a period bridging pre-parturition and post-parturition, said efficacy being in terms of the influence of the RPAA feeding and its period upon milk production.

The feeds used are shown in Table 3.

                  TABLE 3     ______________________________________     Feed Compositions and Feeding Amounts (kg/day)              Low protein feeds                            High protein feed              (low protein TMR)                            (high protein TMR)              CP12  CP14    CP16    CP19     ______________________________________     Corn silage                10.0    6.0     8.3   8.3     Beatpulp                   0.7   0.6     Alfalfa hay                4.4   4.4     Grass hay  5.0     2.5     Corn               2.8     6.8   6.6     Soybean meal       0.4     1.1   1.0     Corn gluten meal           1.1   1.4     Blood meal         0.4           0.5     Molasses                   0.3   0.3     Urea               0.05     Inorganic substances                        0.01    0.8   0.8     ______________________________________

where TMR is total mixed ration.

The 30 cows were divided into 3 groups of the same number, the groups being designated Groups A, B and C, respectively. Groups A and B were treated according to the present invention, while Group C was control-treated.

In greater detail, all the cows were fed the low protein TMR: CP12 (CP and 12 referring to crude protein and its content in terms of weight %, respectively) each day beginning 6 weeks prior to their scheduled parturition date for 3 weeks. The Groups A and B cows were fed the low protein TMR: CP14 together with RPAA (50 g/day), while the Group C cows were fed the low protein TMR: CP14 alone, each day beginning 3 weeks parturition. The Group A cows, the Group B cows and the Group C cows were fed the high protein TMR: CP19 together with RPAA (50 g/day), the low protein TMR: CP19 together with RPAA (50 g/day), and the high protein TMR: CP19, respectively, each day beginning with the parturition day for 70 days. Thereafter, the Groups A and C cows were fed the high protein TMR: CP19 alone, while the Group B cows were fed the low protein TMR: CP16 alone. The RPAA had been prepared as in Example 3.

The results are shown in Table 4.

                  TABLE 4     ______________________________________     Lactation period Early     Middle  Late     (weeks)          1-10      11-20   21-44     ______________________________________     Feed amount (DM kg/d)     Group C          18.26     21.71   19.73     Group A          18.95     22.01   19.85     Group B          21.65     22.42   22.27     Milk production (kg/d)     Group C          31.02     26.34   19.28     Group A          35.96     35.59   22.93     Group B          34.27     30.75   22.53     Milk protein production (kg/d)     Group C          0.96      0.80    0.65     Group A          1.09      1.01    0.77     Group B          1.07      0.94    0.76     Milk fat production (kg/d)     Group C          1.24      0.94    0.71     Group A          1.31      1.10    0.81     Group B          1.17      1.01    0.80     ______________________________________

From Table 4, the following are evident:

The RPAA-fed groups (Groups A and B) showed an increased milk production compared to the RPAA-nonfed group (Group C), which in turn manifests the efficacy of being fed a rumen-protected amino acid (RPAA). Groups A and B gave increases of 1452 kg and 1074 kg, respectively, in milk production throughout the whole lactation period, compared to Group C, which in turn means about 15-20% more milk production compared to RPAA being not fed.

Groups A and B gave increases of 119 kg and 817 kg, respectively, in milk production throughout the remaining lactation period after RPAA had been removed from the diet, compared to Group C, which in turn means also about 15-20% more milk production compared to RPAA being not fed. I.e., a rumen-protected amino acid (RPAA) is effective in increasing milk production, and this positive effect continues after RPAA is removed from the diet during the lactation period (residue effect of RPAA supplementation), whereby the increased milk production may be stably maintained for RPAA-fed cows after RPAA is removed.

Also, with respect to milk quality, the RPAA-fed groups gave increases in protein and fat contents, respectively, in the milk, compared to the RPAA-nonfed group. Therefore, the efficacy of being fed a rumen-protected amino acid (RPAA) has been evidenced not only in the amount of milk production but the quality of the milk produced.

Example 6

(1) Preparation of rumen-protected amino acids (RPAA):

To a homogenizer were added 225 g of L-lysine hydrochloride, 270 g of melted hardened beef tallow and 50 g of lecithin (a surfactant), and mixed in such that the L-lysine hydrochloride was well dispersed in the hardened beef tallow matrix. The mixture was sprayed by compressed air and cooled, whereby spherical hardened beef tallow granules (diameter, about 5 mm) were obtained with the hydrochloride being dispersed homogeneously therein. Such spherical hardened beef tallow granules will be referred to as RP-Lys.

The L-lysine content in the RP-Lys granules was determined by boiling 5g of sample granules in 100 ml of water until the granules were melted, followed by subjecting the resulting mixture to amino acid analysis using an automatic amino acid analyzer.

50g of the RP-Lys granules (a feed additive) was shaken in 1,000 ml of distilled water at 39° C. for 6 hours, and it was revealed that more than 75% of the L-lysine hydrochloride was retained in the hardened beef tallow matrix. On the other hand, the same procedure was repeated except that a pepsin-pancreatin buffer was used instead of the distilled water, to reveal that more than 80-90% of the L-lysine hydrochloride was dissolved out of the matrix.

DL-methionine was treated in the same manner, and gave spherical hardened beef tallow granules with the DL-methionine being dispersed homogeneously therein, which granules will be referred to as RP-Met.

(2) Feeding experiment with or without RPAA:

10 multiparous, lactating dairy cows from Nasu district, Tochigi prefecture, Japan, were fed a common diet for the first 5 weeks postpartum for standardization.

They were divided into two groups of the same number as shown in Table 5, the RPAA-fed group consisting of Cows E1-E5 and the RPAA-nonfed group (Control) consisting of Cows C1-C5, depending on milk production, milk fat percentage and milk protein percentage in the 5th week postpartum, parousness, parturition date, and performances in the last lactation period. In FIGS. 7 and 8, there are given the Wood curves of Cows C1-C5 and Cows E1-E5, respectively.

                                      TABLE 5     __________________________________________________________________________     Experimental Animals                                             Average Milk                           Last Lactation                                    Total Milk Produc-                                             Production     Birth   Age as of                      Parturi-                           Peaks    tion in Last Lac-                                             in Week 5        Date Parturition                  Parous                      tion Date                           Milk                               Milk Fat                                    tation(*1)                                             postpartum     Cows        (Y/M/D)             (Y/M)                  (Times)                      (M/D)                           (kg/d)                               (%)  (kg/305d)                                             (kg/d)     __________________________________________________________________________     RPAA-nonfed Group (Control Group)     C1 `58.11.16             4/6  3    5/10                           45.2                               3.3  9594.7   39.8     C2 `58.2.14             5/3  4   6/2  45.0                               2.8  9156.4   41.7     C3 `58.1.26             5/4  4    6/13                           42.8                               3.3  9497.2   37.2     C4 `58.6.1             7/1  6    7/13                           37.0                               3.4  8326.1   37.4     C5 `59.2.18             4/6  3   8/5  38.9                               3.6  9351.9   44.1     (Average)    (4.0)    (41.8)                               (3.3)                                    (9185.3) (40.0 ± 2.9)     RPAA-fed Group (Experimental Group)     E1 `59.2.25             4/3  3    5/18                           36.8                               4.0  9057.2   43.7     E2 `58.3.1             5/2  4   6/9  47.0                               3.7  10091.0  43.5     E3 `59.2.13             4/4  3    6/12                           35.0                               3.2  8141.1   38.5     E4 `59.2.6             4/5  3    6/30                           37.3                               3.7  7991.9   38.3     E5 `59.8.2             4/0  3   8/5  37.0                               3.3  7878.0   36.7     (Average)    (3.2)    (38.5)                               (3.6)                                    (8631.8) (40.1 ± 3.2)     __________________________________________________________________________      (*1)Wood Curveestimated values

Then, the experimental group cows received the commnon diet supplemented with RPAA from 6 to 17 weeks postpartum. Throught the remaining lactation period, the RPAA was removed from the diet. Compared therewith, the control group cows continued to receive the common diet only, throughout the whole lactation period.

As the results, as will be seen from Table 6, the experimental group continued to give more milk production than the control group, both in the middle stage (from 18 to 31 weeks postpartum) and in the late stage (from 32 to 44 weeks postpartum), which is attributable to the "residue effect" of the RPAA supplementation for the early stage (6 to 17 weeks postpartum).

                  TABLE 6     ______________________________________     Total Milk Production(*1)                Average (S.V.)                  Control   Experimental                                      Improvement                  Group     Group     Weight (%)     Lactation Stage                  kg/cow    kg/cow    kg/cow (%)     ______________________________________     Early Stage (from                  3046.6    3037.5    -9.1 (-0.3)     6 to 17 weeks post-                  (95.1)    (76.5)     partum); 12 weeks     (84 days)     Middle Stage (from                  2754.3    2925.8    171.5 (6.2)     18 to 31 weeks                  (212.5)   (87.7)     postpartum); 14     weeks (98 days)     Late Stage (from                  1855.0    2087.6    232.6 (12.5)     32 to 44 weeks                  (181.7)   (415.9)     postpartum); 13     weeks (91 days)     ______________________________________      (*1)Average after corrected on the basis of the milk production in Week 5      postpartum.

Incidentally, the 10 cows were different in their milk production background from one another. In order to properly evaluate the effects of RPAA supplementation with the use of such cows, it was desirable that they were separated into an Experimental Group (an RPAA-fed group) and a Control Group (an RPAA-nonfed group), and that the 2 groups should preferably produce almost the same amounts of milk when they were not fed an RPAA. For these reasons, the cows were fed a common diet for 5 weeks postpartum, during which their milk production was observed and interpreted, and divided into the 2 groups as shown in Table 5.

The start date in this Example of the RPAA supplementation of 6 weeks postpartum was only for the purpose of experiment. In practice, such start dates of course do not always need to be as late as 6 weeks after calving and can be somewhere prior to calving, insofar as RPAA administration periods stop somewhere within 5 months into the lactation period. According to the present invention, increases in milk production may be maintained still after RPAA is removed from the diet by the "residue effect".

The following is to be added to help understand the experiment.

Concerning the experimental animal used, there are given in Table 5 their individial subject number, birth date, age, parousness, parturition date, milk production peak in the last lactation, total milk production in the last lactation estimated on the basis of curve, and the average milk production in Week 5 postpartum.

The RPAA used were the RP-Lys and RP-Met as prepared under (1) above. They were L-lysine hydrochloride and DL-methionine dispersed in spherical hardened beef tallow matrices, respectively.

The RP-Lys and RP-Met were added to the diet shown in Table 7 in amounts of 16 g and 6 g in terms of lysine and methionine to be absorbed in the small intestine, respectively, and administered to the experimental group animals every morning for from 6 to 17 weeks postpartum. Control treatment was carried out by repeating the above procedure with the exception that neither RP-Lys nor RP-Met was added.

In Table 8 is shown the composition of the mixed diet in Table 7.

                  TABLE 7     ______________________________________     Diet Composition               Amounts of Diet (kg/d)               Milk Production     Meterial    when 40 kg/d                            when 30 kg/d                                       when 20 kg/d     ______________________________________     Corn silage 14.0       10.0.      10.0     Thimothy hay                 4.0        4.0        4.0     Lucerne hay 3.0        3.0        3.0     Hay cube    2.0        2.0        2.0     Mixed diet  15.4       13.0       8.0     Roasted soybean                 0.3        0.3        0.3     Total       38.7       32.3       27.3               Components     Dry mater intake (kg)                 25.2       22.0       27.6     DMI/body wt. (%)                 3.87       3.38       2.71     TDN (% of DM)                 72.4       71.7       68.9     CP (% of DM)                 16.1       16.2       15.4     CF (% of DM)                 16.2       16.9       19.7     Ca (% of DM)                 0.77       0.79       0.79     P (% of DM) 0.50       0.50       0.42     Roughage/Concentrate                 45:55      47:53      59:41     ratio     ______________________________________

                  TABLE 8     ______________________________________     Composition of the Mixed Diet     Material           kg/d   %     ______________________________________     Corn               8.5    55.0     Soybean meal       1.7    10.9     Beet pulp          2.3    15.0     Corn gluten meal   0.9    5.8     Rice bran          0.6    4.2     Wheat bran         0.4    2.6     Rapeseed meal      0.3    1.6     Dicalcium phosphate                        0.34   2.23     Calcium carbonate  0.09   0.59     Sodium chloride    0.17   1.08     Vitamin/mineral mix                        0.15   1.00     Total              15.43  100.00     CP (% of DM)       19.17     CF (% of DM)       5.37     TDN (% of DM)      82.82     ______________________________________

The mineral mix contained 30 g of magnesium, 149 g of potassium, 1.65 g of copper, 8.60 g of zinc, 4.17 g of manganese and 0.16 g of iodine, per 1 kg of the mix, while the vitamin mix contained 50,000 IU of vitamin A, 5,000 IU of vitamin D₃ and 300 mg of the acetate of dl-α-tocopherol per 1 g of the mix.

Each cow was twice milked everyday, i.e., in the morning and in the evening, and the combined milk production was the milk production (kg/day) of the day concerned. With respect to each cow, their total milk production was calculated, while with respect to each group, their average total milk production was calculated.

Supplementing cows with RPAA is an effective means of increasing the yield of milk, milk protein, milk fat, etc. compared to unsupplemented cows. In fact, RPAA-supplemented cows produced numerically more milk than cows supplemented with much higher levels of bypass protein. Thus RPAA Supplementation is an effective method of providing cows with essential amino acids. This technology will aid dairy producers through increased milk production and decreased feed costs. Rumen protected amino acids will have a positive environmental impact in that they will allow cows to produce the same amount or more milk than a diet much higher in dietary crude protein. This, in turn, will reduce the quantity of nitrogen excreted in manure and the risk of groundwater pollution. 

What is claimed is:
 1. A method for increasing amino acid levels in ruminant animals comprising feeding said animals a mixture of base feed and a rumen-protected feed additive, said feed additive consisting of rumen-protected lysine, or a rumen-protected mixture of lysine and methionine, each day beginning approximately 3 weeks prior to the scheduled parturition date of said ruminant animal and continuing said feeding for at most approximately five months into the lactation period of said animal, wherein said feed additive is added to said base feed in an amount sufficient to provide that amount of lysine or lysine and methionine required by said animal, wherein said increased amino acid levels are maintained for at least 23 weeks after removal of said rumen-protected feed additive.
 2. A method for increasing amino acid levels in ruminant animals comprising feeding said animals a mixture of base feed and a rumen-protected feed additive, said feed additive comprising rumen-protected lysine, or a rumen-protected mixture of lysine and methionine, each day beginning approximately 1 day after parturition and continuing said feeding for at most approximately five months, with minimum administration time of two days into the lactation period of said animal, wherein said feed additive is added to said base feed in an amount sufficient to provide that amount of lysine or lysine and methionine required by said animal, wherein said increased amino acid levels are maintained for at least 23 weeks after removal of said rumen-protected feed additive.
 3. A method for increasing amino acid levels in ruminant animals comprising feeding said animals (a) a low protein feed each day beginning approximately 6 weeks prior to the scheduled parturition date of said ruminant animal, (b) a feed having between a low and middle protein content, together with, or without, a rumen-protected feed additive comprising lysine or a mixture of lysine and methionine each day beginning between approximately 4 weeks and approximately 1 week prior to said scheduled parturition date, (c) a middle protein feed together with said rumen-protected feed additive each day beginning the parturition day of said animal for a period of between approximately 4 weeks and approximately 5 months, and (d) a middle protein or high protein feed each day during the remaining lactation period of said animal, wherein said low, middle and high protein feeds contain protein in amounts of 10-14% by weight, 15-17% by weight and 18-22% by weight, in terms of crude protein, respectively.
 4. A method as claimed in claim 1, wherein said feeding into the lactation period is continued from 30 days to approximately five months.
 5. The method as claimed in claim 1, wherein said animals are fed each day beginning approximately 3 weeks prior to the scheduled parturition date of said ruminant animal, and wherein said feeding is continued for 70 days into the lactation period of said animal.
 6. The method as claimed in claim 1 wherein said animals are fed a mixture of base feed and a feed additive, said feed additive consisting of a rumen-protected mixture of lysine and methionine.
 7. The method of claim 1, wherein said feed additive consists of rumen-protected lysine.
 8. The method of claim 2, wherein said feed additive consists of rumen-protected lysine.
 9. The method of claim 3, wherein said rumen-protected feed additive comprises lysine. 